Air-cooled condenser

ABSTRACT

An air-cooled condenser in which pipes extending between an upper header and a lower header are divided into upper and lower axial sections by the upper ends of condensate tubes which lead downwardly to a condensate chamber. Steam is supplied through the headers to opposite ends of the pipes and condensate from the upper section of each pipe draining down the respective tube to the condensate chamber which condensate from the lower section of each pipe drains into the lower header. A fan causes cooling air to pass over the pipes which, for efficient heat transfer, may be finned.

United States Patent Dietrich Dolmt Inventor Berlin, Germany Appl. No.859,829 Filed Sept. 22, 1969 Patented Oct. 12, 1971 Assignee BorsigGesellschaft mit beschrankter Haftung Berlin, Germany Priority Sept. 25,1968 Germany P 17 76 130.7

AIR-COOLED CONDENSER 10 Claims, 3 Drawing Figs.

US. Cl 165/111, 165/174, 62/289, 62/290 Int. Cl F281 13/04 Field ofSearch 165/111,

174, 175, 110; 159/28; 202/185, 185 B; 62/289, 290,DIG. 16

[56] References Cited UNITED STATES PATENTS 1,890,185 12/1932 Lucke165/175 X 3,450,197 6/1969 Fieni 165/174 X FOREIGN PATENTS 255,445Germany 165/174 908,429 Great Britain 165/1 1 1 PrimaryExaminer-Frederick L. Matteson Assistant Examiner-Theophil W. StreuleAtt0rney-Walter Becker ABSTRACT: An air-cooled condenser in which pipesextending between an upper header and a lower header are divided intoupper and lower axial sections by the upper ends of condensate tubeswhich lead downwardly to a condensate chamber. Steam is supplied throughthe headers to opposite ends of the pipes and condensate from the uppersection of each pipe draining down the respective tube to the condensatechamber which condensate from the lower section of each pipe drains intothe lower header. A fan causes cooling air to pass over the pipes which,for efficient heat transfer, may be AIR-COOLED CONDENSER The presentinvention relates to a condenser which is cooled by an automaticallymoved airflow, and in which there are provided at least two rows ofsubstantially parallel condenser pipes spaced from each other andlocated one behind the other when looking in the direction of flow ofthe cooling air. More specifically, the present invention concerns anaircooled condenser of the above-mentioned type in which the rows ofcondenser pipes are in parallel arrangement connected tosteam-distributing chambers common thereto and are in communication withcondensate collecting chambers. The round or profiled condenser pipes,which are in most instances of the same design, are, as a rule, equippedwith fins. On the outside, the condenser pipes are acted upon by a coolairflow which is drawn from the atmosphere and is automatically put intomotion by a fan.

Generally, condensers are so operated that the stream to be condensedflows from the top into or about the pipes, and the condensate flows inthe direction of the steam downwardly into the condensate collector.

Air-cooled condenser installations of the above-mentioned type,especially such for depositing turbine exhaust steam with finned pipebundles which at the upper end are connected to a commonsteam-distributing pipe system so that the steam and the condensate ineach pipe can flow inone direction only, namely, from the topdownwardly, and with cooling air temperatures below the freezing pointcause considerable disturbances in the operation for instance in thevacuum installation. With turbine exhaust steam, for instance, thecondensation temperature is generally at 60 C. and in most instanceseven lower which means that the temperature distance between the watersteam condensate and the freezing point thereof is relatively small. Thecondensate flows along the inner pipe wall downwardly to the mouth ofthe pipe into the condensate chamber. In view of the very unfavorableheat passage conditions between the condensate and the cooling air inthe lower portion of the pipes, also air under certain conditions ofoperation, a steam condensation no longer occurs, with low outer airtemperatures also a low temperature of the pipe wall occurs. On theother hand, with low outer air temperatures also the temperaturedistance between exhaust steam and cooling air is relatively great. Thisbrings about that the condensation is completed at a greater distancefrom the lower pipe mouth than for instance at the point for which theinstallation was designed, whereas the condensate with a formingtemperature of for instance 60 C. has to overcome this relatively longpath along the cold inner pipe wall, which means that the condensate hasa long staying time in the unfavorable cooling zone. ln the lower pipesection, the condensate conveys its heat up to solidifying to the coldpipe wall.

It is a well-known fact that the icing danger is greatest in the firstpipe row when looking in the direction of flow of the cooling air,because here the temperature drop between steam and cooling air isgreater than in the pipe rows therebehind. This means that thecondensate stays particularly long in the first pipe row in theunfavorable cooling zone. Similar remarks also apply to the partial loadoperation for instance of a condensation turbine. The condensation ofthe exhaust steam may in this instance be completed soon after the steamenters the upper pipe mouth because the excessive cooling surface willunder partial load operation have such an effect that the major portionof the lower section of the cooling surface is not contacted by theexcess steam. Also in this connection, the condensate has to pass over alarger under cool surface. A control of the quantity of cooling air orthe turning off of cooling surfaces may at less low outer airtemperatures result in a slight improvement, however, at surroundingtemperatures approximately from -5 C. on, the less mentioned step is noteffective against formation of ice in the pipes. Noncontrollable windinfluences increase the icing danger in winter considerably.

lce formation in the lower pipe mouth brings about an increase inpressure in the condenser and considerably reduces the vacuum.

Ice plugs which may form may even burst the pipes with the result thatair will break in. Under certain circumstances, it may then be necessaryto disassemble the installation.

Condensers have become known in which the exhaust steam line is soarranged that the steam can enter the mouth of the finned pipes onlyfrom below, and in which the condensate flows downwardly incountercurrent flow to the upwardly flowing steam, into the condensatecollecting chambers. This arrangement of the exhaust steam line, whichis also known as dephlegmatoric circuit, prevents the undercooling ofthe condensate by the fact that the upwardly flowing warm steam keepswarm the condensate which flows in opposite direction. However, thiscircuit can be employed only under certain conditions of operation, butwherever it can be employed, it will safely prevent ice formation in thepipes. This dephlegmatoric ,circuit, however, as already indicated, canbe employed only under certain conditions when the proper function ofthe condenser installation is to be assured. In this connection, it hasto be taken into consideration that the speed of the steam when flowinginto the lower mouth of the pipes is not very high. Too high steamvelocities bring about an accumulation of the downwardly flowingcondensate in the mouths of the pipes. Variations in the pressure in thecondenser and shockwise flowing off of the liquid and thereby anirregular operation for instance of a vacuum installation will result.Admissible inflow speeds require a relatively small specific volume ofthe steam to be condensed or a correspondingly high inlet cross sectionof all mouths of the pipes. Vacuum steam, especially turbine exhauststeam, however, has a relatively large specific steam volume so that theinlet cross section of all mouths or exits of the pipes must be verygreat in order to make possible a corresponding inlet speed of the steamduring full load operation. Large inflow cross sections, however,require short pipes and a constant cooling surface. It is a well-knownfact that devices and therefore air-cooled condensers with relativelyshort pipes have the drawback that for instance a considerable number ofchambers, long pipelines and a plurality of fans increase the cost ofthe installation and make the same uneconomical.

On the other hand, the construction of a condenser with such short pipesis frequently not possible at all because with such short pipes aneconomic relationship with regard to the diameter of the fans cannot berealized. It is for this reason that the dephlegmatoric operation isfrequently not possible at all.

There have also become known condenser installations with nozzles whichare inserted into the pipe bottom of the steam distributing chamber ordirectly into the pipes. These nozzles, when looking in the direction ofthe cooling airflow have their cross-sectional passage for the steamdecreasing successively so that a better distribution of the steam overthe individual rows of pipes will be obtained and the pressure drop inthe rear rows of pipes will be increased. For certain definiteconditions of operation, it is possible by such an arrangement to bringabout that in the rows of pipes which are first acted upon or passedthrough by the cooling air, the condensation of the steam is completedonly shortly in front of those areas where the pipes lead into thecondensate collecting chamber so that an undercooling of the condensatewill be avoided. However, with such air-cooled condenser equipped withnozzles, it is not possible to adapt the arrangement to the respectiveconditions of operation in such a way that in particular at low-coolingtemperatures and low steam loads, the icing danger will be eliminated,because in view of the excessive cooling surface, the condensation ofthe steam is completed far away from the lower mouth of the pipes.Furthermore, the nozzles bring about a considerable pressure loss at thesteam side and thus create a poor vacuum. Furthermore, an air-cooledcondenser installation has become known in which the condenser chambersprovided at the lower end of the pipe bundle are in the direction offlow of the cooling air subdivided into individual subchambers. Thesefinned pipe bundles, in which the steam flows from the top downwardlywhile condensing, have associated therewith dephlegmator bundles whichon the air side are parallel to each other and on the steam side arearranged one behind the other. These subchambers are individually andadjustably connected to the air suction devices. Such an arrangement issupposed to bring about that the underpressure in the succeedingsubchambers decreases in the direction of the airflow whereby the steamdistribution is, in conformity with the pipe rows, connected to theindividual subchambers in conformity with the respective availabletemperature drop between steam and cooling air. The condensation issupposed in this way to be completed in all pipe rows at a slightdistance from where the pipe ends lead into the pertaining subchambers.Such an arrangement has the drawback that the exhaust steam condensesfirst from the top in downward direction and only subsequently theresidual steam passes into the dephlegmator. It will be evidenttherefrom that with partial load operation, for instance, a condenserturbine, and at low cooling temperatures, an excessive cooling surfaceis obtained in the condenser portion which with regard to the steam sideis located in front. This cooling surface completes the condensation ofthe exhaust steam not at a short distance from where the pipe ends leadinto the lower chambers but at a considerable distance therefrom Thecontrollable air suction device will definitely not remedy the situationbecause with said air suction devices it is possible only to maintainthe condensation in the individual pipe rows approximately equal. Underno circumstances is it possible by means of the air suction device todisplace the condensation downwardly which has been completed at aconsiderable distance from the lower pipe mouth. Consequently, also withthe condenser equipped with these devices, the desired effect cannot berealized. A further drawback consists in that expensive and sensitivecontrol devices are necessary for the air withdrawal.

It is, therefore, an object of the present invention to provide anair-cooled condenser which will overcome the above mentioned drawbacks.

It is another object of this invention to provide an air-cooledcondenser, in which the condensation of the steam is effected in twospaced sections with clear flow relationship in the pipes in flowdirections which are opposite to each other. The length of the pipe upto the condensate discharging means in the upper subsection of thefinned pipe bundle is relatively short so that also the undercoolingdistance at very low cooling temperatures will be reduced to a minimum.

These and other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawings, in which:

FIG. 1 diagrammatically illustrates a condenser.

FIG. 2 represents a section taken along the line ll-ll of FIG. 1.

FIG. 3 represents a cross section through a condenser element on alarger scale than that ofFlG. 1.

The condenser according to the present invention is characterizedprimarily in that the steam-distributing chambers and pipelines at theupper end of the finned pipe bundle, and the steam distributor andcondensate collecting chambers combined at the lower end are soconnected to the bypass lines that the steam flows through the finnedpipes in countercurrent direction while the finned pipes spaced at acertain distance from the upper and lower mouths of the pipes aresubdivided transverse to the pipe axis into pipe sections by means ofcondensate withdrawing means which are connected to the central pipeswhich latter lead into the condensate collecting chamber. In this way,the condensation of the steam is effected in two separate subsectionswith clear flow conditions in the pipes in countercurrent flowdirection. The pipe length up to the condensate withdrawing line in theupper partial section of the finned pipe bundle is relatively short sothat also the undercooling distance will be reduced to a minimum atlow-cooling air temperatures. The condensate is detached from the upperpipe section before it is undercooled and might ice. This detachmentfrom the inner pipe wall is effected by the condensate withdrawal means,and the detached condensate passes through the central pipescountercurrent to the upwardly flowing warm steam in the dephlegmatorpart, and is here held warm by the steam, which is extremelyadvantageous.

A further advantage by subdividing the finned pipe in a directiontransverse to the pipe axis in two separate subsections and by thebilateral steam action consists in that the steam has available a pipesection which is large (approximately twice as large) as is availablewith the heretofore known condenser designs. As a result thereof, theloss in pressure of the steam when flowing into the mouth of the pipesis reduced and thereby an economic vacuum is realized. Particularlyduring the summer season, the heretofore known condensers have a poorvacuum because they lack the abovementioned advantage.

It is further advantageous at reduced quantity of steam, to keep onlythe dephlegmator part in operation which is particularly suitable inthis connection inasmuch as it prevents the freezing of the condensate.Also when in this instance, i.e. at a low steam quantity, still somesteam should come in from above, the path through the pipe bundle panwhich is operated as a condenser is shorter than is the case with heretofore known designs requiring the entire or full-pipe length.

A further important advantage of the present invention over heretoforeknown structures consists in that not only the steam side is separatedbut also the condenser side. Due to the fact that a portion of thecondensate is separated by the central pipes from the condensate flowingoff from the dephlegmator part, an accumulation of condensate in thelower pipe mouth, i.e. at the steam inlet of the dephlegmator is avoidedfor all practical purposes.

With the present design, no control elements and shutoff devices arenecessary which at temperatures below the freezing point are necessarywith the heretofore known designs in order to prevent freezing.

A further development of the present invention consists in that the pipesections, measured from the condensate withdrawal means to therespective pipe mouth in the lower as well as in the upper pipe sectionsprior to flowing into the pipe mouth are so designed that they becomegreater in steps. in view of this stepwise greater configuration, itwill be assured that where the steam enters the finned pipe bundles, theshortest pipe length and thereby the smallest cooling surface isavailable to the incoming steam. The finned pipe bundles which arelocated farthest from the steam entry have, when viewing in the flowdirection of the steam, the larger cooling surface. At full-load andrelatively large inflow speed of the steam, the actuation on the steamside in the individual finned pipe bundles is distributed better due tothe fact that between the inflowing steam and the finned pipe bundlesremote therefrom, with the increasing cooling surfaces, an ever greaterpressure drop will form. This brings about that the nonuniform flowconditions of the steam in the distributing chambers or pipelines andthe different pressure losses in the pipe mouths are equalized withregard to each other.

With small quantities of steam, however, the steam is condensed only inthe lower dephlegmator part. As a result thereof, it will be realizedthat a residue steam quantity will penetrate the connecting pipes andpass into the condenser operated pipe bundle part whereby the safety ofoperation will be increased.

If the inflow velocity of the steam, contrary to the just describedinstance, is relatively small, it will be understood that a stepping ofthe cooling surface also in the inverse direction may be effected inconformity with the present invention so that the fin pipe mouths whichare the first when looking in the steam direction are actuated open tothe same extent by the said operation as are the finned pipe mouthslocated therebehind.

According to a further feature of the invention, the bores are arrangedslightly below the condensate withdrawal means in the central pipes sothat from the lower condensate collecting chamber, the inert air iswithdrawn from the upper subsection of the pipe through the pipe mouthof the central pipes in the condensate withdrawing means, as well asfrom the lower subsection of the pipes through the bores, and thewithdrawn inert air then passes through the central pipe. In view ofthis arrangement of the bores, the dephlegmator chamber or coolingsurface is better taken advantage of so that the condensate withdrawingmeans will be kept warm at this area.

It is known that the condensation in the first row of pipes when viewingin the cooling airflow direction is completed at a larger distance fromthe lower pipe mouth than is the case with the pipe rows therebehind.According to a further development of the invention, the pipe sectionsmeasured from the condensate withdrawing means to the pipe mouth in theupper steam distributing chamber when seen in the flow direction of thecooling air is in each pipe row designed longer. By shortening the frontpipe rows of the part operated as condenser, the condensate withdrawingmeans are closer to the end of the condensation, and the path of thecondensate along the cold pipe inner wall is reduced and is earlierintroduced into the central pipes in the warm dephlegmator part. In thelast row of pipes when viewing the arrangement in the airflow direction,the cooling surface in the part operated as a condenser is so large thatthe steam does not penetrate the central pipes of the dephlegmator partbut is already condensed. As a result thereof, optimum design of theinstallation will be assured.

In order to be able to equalize different temperature expansions of theindividual pipes, the central pipe is, in conformity with the presentinvention, built up of two parts. The lower part with a larger diameteris connected to the combined steam distributor and condensate collectingchamber and overlaps the upper portion of the central pipe.

Referring now to the drawings in detail, the condenser illustrated inFIGS. 1 and 2 comprises a plurality of roof-shaped condenser elementswhich are formed of at least one or, as illustrated, of three rows ofsubstantially parallel finned pipe bundles l which are spaced from eachother or are arranged one behind the other when viewing in the flowdirection d of the cooling air. Steam from below is conveyed to thefinned pipe bundles 1 through the lower combined steam producing andcondensate collecting chamber 5. Through the conveying lines 3 and steamlines 2, also steam from above is conveyed to the finned pipe bundles l.The pipe bundles are thus passed through by the steam in oppositedirection. However, it is also obvious that, if desired, the exhauststeam conduits may be connected to the finned pipe bundles in such a waythat a portion of the steam is condensed first in the upper pipesections and the residual steam is condensed in the lower pipe sections.The supply of steam may also be effected (in a nonillustrated manner)from a gable side (FIG. 1) through only one bypass line 3 in such a waythat the steam acts upon the upper and lower pipe sections parallel orin series and passes therethrough in opposite direction in conformitywith the invention. The pipes are, by a condensate withdrawing means 14,subdivided on the inside transverse to the pipe axis into an uppersection 12a and a lower section 12 b. The steam fed from above throughthe steam distributing chambers 4 will condense in the upper pipesection 12a, and the condensate will flow through the condensatewithdrawing lines 14 and central pipes into the condensate collectingchambers 8.

The steam which flows from the combined steam distributor and condensatecollecting chambers 5 upwardly will condense in the lower pipe sections12b, and the condensate will flow back into the above-mentionedcondensate collecting chambers 5. The condensate is withdrawn from thecondensate collecting chambers 5 and 8 through the pipes 9 andcondensate lines 10, respectively, in the direction of the arrow b. Theinert air from the lower pipe sections 12b is, through bores 13, locatedshortly below the condensate withdrawing lines 14 in the central pipes15, withdrawn together with the inert air from the upper pipe sections120 through the central pipes 15, the condensate collecting chambers 8,and pipes 6 into the air lines 7 in the direction indicated by the arrow0. FIG. 1 further shows the bulkheads ll of the air condensator which issupported by four supports 17 illustrated at the lower end.

FIG. 1 furthermore illustrates that the pipe sections, measured from thecondensate withdrawing line 14 to the respective mouth of the pipesincrease by steps or continuously not only in the upper but also in thelower pipe sections 12a and 12b when viewed in the flow direction a ofthe steam. The pipe sections measured from the condensate withdrawingmeans 14 to the respective pipe mouth not only in the upper but also inthe lower pipe sections 12a and 12b when viewed in the flow direction aof the steam may be designed stepwise smaller (not illustrated).

FIG. 2 shows that the roof-shaped finned pipe bundles l have a crosssection forming the sides of an approximately equilateral triangle thebasis of which is formed by an axial fan 18. The fin-equipped pipebundles may also be so arranged that in the direction of the pipe axisthey are perpendicular with regard to the horizontally arranged fan axis(not illustrated). Above the axial fan 18 there is provided atransmission 19 and a motor 20. As indicated by the arrows d, thecooling air is, by at least one axial fan 18, conveyed from the bottomin upward direction or in reverse direction (not illustrated) and passesby the outside of the smooth or finequipped bundle 1.

FIG. 3 shows the subdivision of the upper pipe sections 12a which, whenviewed in cooling airflow direction d are longer in each pipe row. Thecondensate withdrawing means 14 is thus arranged closer to thecondensation end in the upper pipe section 1211, because the latter isdisplaced as is well known in downward direction when viewing the flowdirection of the cooling air. Thus, the path of the condensate along thecold inner wall of the pipe section is reduced in those pipe rows which,when viewing the direction of flow of the cooling air, are located infront. The central pipe 15 comprises two parts. The lower part 16 with alarger diameter is connected to the combined steam distributor andcondensate collecting chamber 5, and the upper part of the central pipe15, which has a smaller diameter, is covered up by said lower part 16 insuch a way that therebetween a labyrinthlike sealing effect is obtained.This subdivision of the central pipe compensates for the temperatureexpansions of the individual pipes.

It is, of course, to be understood that the present invention is, by nomeans, limited to the particular showing in the drawings but alsocomprises any modifications within the scope of the appended claims.

What is claimed is:

l. A condenser having an upper header means and a lower header means,conduit means connected to said header means for supplying steamthereto, pipe bundle means connected to and extending between saidheader means, and fan means operable for causing cooling airflow throughsaid pipe bundle means, a condensate discharge tube extending into eachpipe of said pipe bundle means from the lower end of the respectivepipe, the upper end of each discharge tube engaging the inside of therespective pipe and dividing the pipe into upper and lower axialsections whereby steam to be condensed flows in countercurrent directionsimultaneously from said header means into both ends of said pipes,condensate chamber means connected to the lower'ends of said tubes toreceive from said tubes the condensate from the upper sections of saidpipes, the condensate from the lower sections of said pipes drawing fromsaid pipes into said lower header means, and means for withdrawingcondensate from said condensate chamber means and from said lower headermeans.

2. A condenser according to claim I in which said steam flows axially insaid header means and the length of said pipe sections varies inincreasing direction in conformity with the length of travel of thesteam prior to entry into pipes along said header means to the end ofthe respective section.

3. A condenser according to claim 1 in which said steam flows axially insaid header means and the length of said pipe sections varies indecreasing direction in conformity with the length of travel of thesteam prior to entry into pipes along said header means to the end ofthe respective section.

4. A condenser according to claim 1 in which steam is supplied to aboutthe middle of the length of said lower header means for flow outwardlytherein toward the ends and flows from the ends thereof to the ends ofsaid upper header means and then toward the middle of the length of saidupper header means. the length of the said sections of said pipes intowhich steam flows progressively increasing in the direction of steamflow prior to entry into pipes through said header means.

5. A condenser according to claim 1 in which each said tube has aperturemeans therein immediately below the region of engagement of the upperend of the tube with the respective pipe whereby inert air from bothcollectively withdrawn axial sections of each pipe passes into therespective condensate discharge tube and downwardly therethrough to saidcondensate chamber means.

6. A condenser according to claim 1 in which said pipe bundle meanscomprise pipe sections longer in differing pipes displaced from eachother in the direction of airflow through the bundle means, the uppersections of said pipes varying in length in the direction of saidairflow.

7. A condenser according to claim 1 in which each of said tubescomprises a first upper portion which at its upper end engages arespective pipe and a second lower portion extending into saidcondensate chamber means, said respective portions being in slidabletelescopic engagement and thereby compensating for differential thermalexpansion of individual pipes in the condenser.

8. A condenser according to claim 1 in which said pipes individually arefinned for each bundle means.

9. A condenser according to claim 1 in which said lower headerinterconnected also to bypass means is in the form of two laterallyspaced lower headers, said pipes converging in the upward direction fromsaid lower headers, said fan discharging air upwardly into the spaceconfined between said pipes and flowing laterally over and between saidpipes.

10. A condenser according to claim 6 in which said upper respectivelysections of said pipes individually increase in length progressively inthe direction of airflow through said pipe bundle means.

1. A condenser having an upper header means and a lower header means,conduit means connected to said header means for supplying steamthereto, pipe bundle means connected to and extending between saidheader means, and fan means operable for causing cooling airflow throughsaid pipe bundle means, a condensate discharge tube extending into eachpipe of said pipe bundle means from the lower end of the respectivepipe, the upper end of each discharge tube engaging the inside of therespective pipe and dividing the pipe into upper and lower axialsections whereby steam to be condensed flows in countercurrent directionsimultaneously from said header means into both ends of said pipes,condensate chamber means connected to the lower ends of said tubes toreceive from said tubes the condensate from the upper sections of saidpipes, the condensate from the lower sections of said pipes drawing fromsaid pipes into said lower header means, and means for withdrawingcondensate from said condensate chamber means and from said lower headermeans.
 2. A condenser according to claim 1 in which said steam flowsaxially in said header means and the length of said pipe sections variesin increasing direction in conformity with the length of travel of thesteam prior to entry into pipes along said header means to the end ofthe respective section.
 3. A condenser according to claim 1 in whichsaid steam flows axially in said header means and the length of saidpipe sections varies in decreasing direction in conformity with thelength of travel of the steam prior to entry into pipes along saidheader means to the end of the respective section.
 4. A condenseraccording to claim 1 in which steam is supplied to about the middle ofthe length of said lower header means for flow outwardly therein towardthe ends and flows from the ends thereof to the ends of said upperheader means and then toward the middle of the length of said upperheader means, the length of the said sections of said pipes into whichsteam flows progressively increasing in the direction of steam flowprior to entry into pipes through said header means.
 5. A condenseraccording to claim 1 in which each said tube has aperture means thereinimmediately below the region of engagement of the upper end of the tubewith the respective pipe whereby inert air from both collectivelywithdrawn axial sections of each pipe passes into the respectivecondensate discharge tube and downwardly therethrough to said condensatechamber means.
 6. A condenser according to claim 1 in which said pipebundle means comprise pipe sections longer in differing pipes displacedfrom each other in the direction of airflow through the bundle means,the upper sections of said pipes varying in length in the direction ofsaid airflow.
 7. A condenser according to claim 1 in which each of saidtubes comprises a first upper portion which at its upper end engages arespective pipe and a second lower portion extending into saidcondensate chamber means, said respective portions being in slidabletelescopic engagement and thereby compensating for differential thermalexpansion of individual pipes in the condenser.
 8. A condenser accordingto claim 1 in which said pipes individually are finned for each bundlemeans.
 9. A condenser according to claim 1 in which said lower headerinterconnected also to bypass means is in the form of two laterallyspaced lower headers, said pipes converging in the upward direction fromsaid lower headers, said fan discharging air upwardly into the spaceconfined between said pipes and flowing laterally over and between saidpipes.
 10. A condenser according to claim 6 in which said upperrespectively sections of said pipes individually increase in lengthprogressively in the direction of airflow through said pipe bundlemeans.